Deep vein thrombosis
From Ganfyd
Contents |
Introduction
Also known as DVT, deep venous thrombosis
Deep vein thrombosis is a manifestation of venous thromboembolic disease (VTE) of which the most serious consequence is pulmonary embolus - a major cause of death and one which is persistently under-suspected and under-prevented.
It is nowadays widely noted to be a major and somewhat avoidable risk after elective surgery. However as it is so common in inpatients most guidelines recommend a routine risk assessment upon admission, both to guide prophylaxis, but more importantly to remind clinical staff to consider the issue.
Diagnosis
By history, examination and special investigation. A high index of suspicion saves lives.
History
Pain in the leg. Particularly following likely predisposing factors such as immobility (operation, travel) systemic inflammation (operation, illness). Ask about previous episodes, IV drug abuse (normally clinically apparent), recurrent miscarriage and family history.
Examination
Unilateral swelling in calf with or without tenderness in the line of the major veins. Diversion of blood flow into superficial veins.
Special investigations
- D-dimer blood level.[1][2]
- Ultrasonography of leg and pelvic veins.
- Xray phlebography with contrast medium (gold standard but less-used now, and not free of hazard).
Risk assessment
A medical algorithm exists - the Modified Wells Score - to assist people in deciding whether to perform ultrasound investigation of the lower limb veins in addition to D-dimer estimation in deciding whether to treat as DVT. Do note that the ultrasound examination used determines what you will find (and treat!). So if you use compression ultrasound (CUS) of proximal veins you need to repeat this in one week if negative. Complete compression ultrasound (CCUS) if used exactly according to protocol has very similar results to venography.[3]
Modified Wells Score calculator
The most cost effective strategy in UK practice, recently defined, is based on a combination of Wells score, D-dimer and ultrasound (with repeat if negative)[4].
There are some interesting risk factors. For example, while dehydration is a risk factor, over-hydration of supine patients (such as the bedridden or those having surgery) causes distension of the deep veins and actually increases radiofibrinogen detectable DVT[5].
Treatment of DVT
Anticoagulation is the main treatment and is also used in thromboprophylaxis.
It has been argued that anti-coagulation of DVTs confined to the lower leg is not necessary. Actually we do not know, as no high quality trials have yet addressed this issue using modern techniques for diagnosis and follow-up so either treatment or no treatment is of unknown effectiveness[6] | The superficial femoral vein is a proximal deep vein so treat thrombosis in it even if your unit does not diagnose and therefore treat distal DVT ! |
Metaanalysis suggests that in patients where anticoagulation was withheld:
- Studies using compression ultrasound (CUS) of proximal veins (Proximal DVT) as criteria for diagnosis had 3-month thromboembolic rate of 0.6% (95% CI: 0.4-0.9%)
- proximal and distal (complete) compression ultrasound (CCUS) (All DVTs) as criteria for diagnosis had 3-month thromboembolic rate of 0.4% (95% CI: 0.1-0.6%) with 50% of these confined to distal veins !
Searching for distal DVT doubles the number of patients given anticoagulant therapy and and a distal DVT has about a sixth the risk of pulmonary embolism from these figures.[7]
Prevention of DVT
See external links below
External links
- NICE guidelines Venous thromboembolism: reducing the risk of venous thromboembolism (deep vein thrombosis and pulmonary embolism) in inpatients undergoing surgery April 2007
- Information for travelers: Risk of venous thrombosis and long distance travel (including air flights) from British Committee for Standards in Haematology (BCSH)
- Sign Publication No 62 Prophylaxis of Venous Thromboembolism October 2002. (ISBN 1899893032.)
- Systematic review of non-invasive diagnostic tests for deep vein thrombosis from Sheffield School of Health and Related Research (ScHARR)
References
- ↑ Wells, Philip S., Anderson, David R., Rodger, Marc, Forgie, Melissa, Kearon, Clive, Dreyer, Jonathan, Kovacs, George, Mitchell, Michael, Lewandowski, Bernard, Kovacs, Michael J. Evaluation of D-Dimer in the Diagnosis of Suspected Deep-Vein Thrombosis. N Engl J Med 2003 349: 1227-1235
- ↑ D-dimer: the test. Labtestsonline web site. Last viewed 14 June 2007.
- ↑ Schellong SM. Complete compression ultrasound for the diagnosis of venous thromboembolism. Curr Opin Pulm Med. 2004;10(5):350-5
- ↑ Goodacre S, Sampson F, Stevenson M, Wailoo A, Sutton A, Thomas S, et al. Measurement of the clinical and cost-effectiveness of non-invasive diagnostic testing strategies for deep vein thrombosis. Health technology assessment (Winchester, England) 2006;10:1-168, iii-iv.
- ↑ Comerota AJ, Stewart GJ, Alburger PD, Smalley K, White JV. Operative venodilation: a previously unsuspected factor in the cause of postoperative deep vein thrombosis. Surgery. 1989 Aug; 106(2):301-8: discussion 308-9.
- ↑ Righini M, Paris S, Le Gal G, Laroche JP, Perrier A, Bounameaux H. Clinical relevance of distal deep vein thrombosis. Review of literature data. Thromb Haemost. 2006;95(1):56-64
- ↑ Righini M, Paris S, Le Gal G, Laroche JP, Perrier A, Bounameaux H. Clinical relevance of distal deep vein thrombosis. Review of literature data. Thromb Haemost. 2006;95(1):56-64
